i have a friend that hired a villa in spain and it had a pool, she swam in it, got back to uk and she is in a very bad way, the doctors can not find anything wrong with her, but she has lost weight, alot of weight and like i said in a very bad way, i live in spain and have not got a pool but i can remember someone telling me about a deadly bug that can live in swimming pools if they are not looked after prop, does anyone out there know the name of this bug, please this is important,

There are many possible diseases and illnesses that can occur from swimming in water that is not properly sanitized. Take a look at this World Health Organization document and look at Chapter 3, Microbial Hazards, for some of the more common problematic bacteria, viruses, protozoa and fungi. Most are not "deadly bugs" (a few are, depending on circumstances) though some can cause serious illness, especially in those with compromised immune systems. I quote selectively from the document in a summary of some of the illnesses below.

I suspect that what you heard regarding a deadly bug was probably the protozoa (an amoeba, actually) Naegleria fowleri that usually kills infected persons in 3-10 days after onset of symptoms. Symptoms of the infection include severe headache, high fever, stiff neck, nausea, vomiting, seizures and hallucinations. This is an extremely rare disease.

Instead, it sounds like your friend might have something else to cause the great loss in weight. This sounds more like the symptoms of the protozoa Giardia where the symptoms include diarrhea, cramps, foul-smelling stools, loss of appetite, fatigue, vomiting and weight loss. Another protozoa, Cryptosporidium, has symptoms of diarrhea, vomiting and abdominal cramps. Symptoms of the bacteria Escherichia coli O157 infection include bloody diarrhea (hemorrhagic colitis) and hemolytic uremic syndrome (HUS), as well as vomiting and fever in more severe cases. Symptoms associated with the bacteria Shigella include diarrhea, fever and nausea. Some enteroviruses (polioviruses, echoviruses, and coxsackieviruses types A and B) have symptoms of vomiting, diarrhea and headache. Noroviruses have symptoms of diarrhea, vomiting, nausea and fever.

Of course, the doctors are the best experts at figuring out what to do and you can refer them to the WHO document if you think it might help.